Hardware Brown spots on electrical plug? Burn, corrosion or what?

[Voltshock R]

Hello. Picture sort of shows the brown spots. Not sure what it is on these electrical plug contacts. I think it came from the device being connected to an old surge protector, so they may be a burn or oxidation.
This one comes up from the middle but most of the other brown spots are just that (and I mean multiple plugs have at least one).
This is probably the worst of it, but was wondering if anyone has suggestion on how to clean or remove the marking(s). I know that brass does not seem to be strong enough to brush it off.
If any other pictures are needed, I'll add them. At the moment it is hard to capture an image properly.
Edit: Changed original image to reflect better view. Also I don't think they are deep scratches, as the surface is smooth on the brown areas.
Thanks for any input.

 

[TotalInsanity4]

Hello. Picture sort of shows the brown spots. Not sure what it is on these electrical plug contacts. I think it came from the device being connected to an old surge protector, so they may be a burn or oxidation.
This one comes up from the middle but most of the other brown spots are just that (and I mean multiple plugs have at least one).
This is probably the worst of it, but was wondering if anyone has suggestion on how to clean or remove the marking(s). I know that brass does not seem to be strong enough to brush it off.
If any other pictures are needed, I'll add them. At the moment it is hard to capture an image properly.
Edit: Changed original image to reflect better view. Also I don't think they are deep scratches, as the surface is smooth on the brown areas.
Thanks for any input.

I've seen this happen to a few of my plugs. I think it's just oxidization that's accelerated by an electrical current, but I'm not really qualified to speak on the matter. All I can say is that my house hasn't burned down yet

 

[Voltshock R]

I see. If oxidation is on ac power plugs, what is probably the best method to remove it without damaging the plug?
I've read 99% rubbing alcohol (with a guess a cloth...maybe a non wet sponge), someone mentioned vinger/salt combo then neutralizing with baking soda, and then there is contact cleaner (which YMMV. The best is suppost to be Deoxit, but they have so many different products. I have no idea which is the version needed, primarily because I am unsure of the metal constitution. Are video game plugs silver/nickel coated? Or are they brass? Is the brown spots enhanced oxidation from burns or is tin leeching?)
I appreciate Totalsanity4's reply; however, it still does not solve the issue.
Would the likely knowledgable person view this question in a different forum. If so, which?

 

[nero99]

you may get a better answer if you ask on tomshardware.com those people there deal with stuff like this a lot

 

[Voltshock R]

Nero99, does one have to make an account with tomshardware.com to ask questions? If not, what are the options to post to them?

 

[nero99]

you need an account. they make it easy to sign up with either just your regular google email or login with facebook options to post questions

 

[Voltshock R]

Thanks for input!

 

[grossaffe]

Maybe it's hard to tell what is going on from the picture, but it doesn't look like anything I'd be worried about.

 

[Mikemk]

It looks too me not like oxidation, but the silver color plating has rubbed off and revealed a different color metal underneath

 

[DinohScene]

The prongs are made from brass and have a silver/chrome plating on them to make them more "attractive?" to the customer.
The repeated contact of the wallsockets and the prongs causes them to rub off and the occasional arch also zaps off the plated part.
It's nothing to worry about when it comes to a firehazard.
if it gets blackened a bit, just get some sandpaper and grind it a tiny bit.

Source: I used to be a electrician.